[xtn]

My one attempt at bleeding the brakes with vacuum - pulling the fluid through from the bleed nipples - was not satisfactory.

#1. The threads of the bleed nipples will let air in.
#2. There is some resistance to fluid flow in the system when it's under vacuum.

This results in air just moving into the caliper via the loosened bleed nipple threads and being sucked right around back into your bleed hose. It just gurgles and minimal fluid flows out. If you accidentally loose vacuum (your hose falls off the nipple for example) you're going to get a bubble of air introduced into the caliper.

I don't know what the resistance to flow is. Perhaps the master cylinder is being sucked into the pressed position, cutting off the open circuit from the reservoir?

xtn